After the flood or the leak, get a dehumidifier. You can rent these from your local hardware store. Keep an eye on it so that you empty it in a timely fashion. But usually there’s more to do. Water damage can be insidious. You must outthink the water, and seek out the hidden places through which the water made a path. (This all presupposes that you have found and eliminated all leaks, leaky pipes, etc.)
That hidden water path is likely to feed mold. You want to remove it completely, because EVEN IF IT IS DRY NOW, if you can see it, there are millions of spores too small for the human eye to detect, and they are just waiting for an opportunity to find the least bit of moisture on cellulose, so they can plant themselves and begin to grow.
And even if they don’t grow right away, the spores themselves cause allergic reactions in some people. And we haven’t even discussed mycotoxins.